The present invention relates to a substrate for thin film magnetic head to be used for the hard disk drive, tape drive, etc. which are the recording apparatuses for computer, and a thin film magnetic head using the same.
As the conventional substrate for thin film magnetic head, there is used a substrate comprising ceramics formed mainly of Al.sub.2 O.sub.3 and TiC, on which amorphous alumina film is formed by sputtering process as ground layer, and its surface is finished into mirror surface with a one-side polishing machine. And, on the resulting ground film, an element is formed by magnetic film to constitute a magnetic head.
The ground film comprising the amorphous alumina film as above is necessary for forming an insulation activity with the Al.sub.2 O.sub.3 --TiC ceramics substrate which are the conductive materials and obtaining a smooth surface. Especially, because the elements are formed with a magnetic film on the ground film, a smoother surface is required. For this purpose, it is now becoming general to make polishing with CMP (Chemical Mechanical Polishing) and the like.
In recent years, in order to improve recording density, there has been introduced MR (Magnetoresistive) using magnetic resistance effect or GMR (Giant MR). And, in order to improve read sensitivity of MR or GMR element, it has become necessary to increase the sense current density, with the result of providing a drawback of easiness to cause heat in the vicinity of the element.
Also, in recent years, in the cases of the MR and GMR heads for hard disk drive, the head floating up amount has become as small as about 1 microinch, or close to the near contact. For this reason, the magnetic head and the medium are liable to slide under contact, and the friction heat produced at this time provides temperature variation of the MR element part of the thin film magnetic head, thereby causing variation of sensitivity. Such a thermal asperity phenomenon has also become a significant problem.
Accordingly, it has been required to improve the heat radiation in the vicinity of the elements of the thin film magnetic head. With the conventional substrate for thin film magnetic head, however, it has not been possible to meet such requirement.